Method for separating electronic components from a composite

ABSTRACT

The invention relates to a method of singulating thin chips from a sawn wafer, comprising the steps of glueing the wafer first onto a carrier and sawing it then into individual chips on said carrier. Subsequently, the chips are detached from the carrier individually or in groups. The method is so conceived that carrier is a rigid board and the adhesive is heat-soluble, the adhesive being deactivated with the aid of heat passing either through the chip itself or through the carrier prior to the detachment of said chips, whereupon the respective chip is detached.

The invention relates to a method of singulating electronic componentsfrom a composite structure, in particular chips from a wafer, whereinthe composite structure is first glued onto a carrier and the componentsare separated from one another, whereupon the components are detachedfrom the carrier individually or in groups making use of a vacuumpipette, the adhesive effect of the adhesive being adapted to be reducedselectively, the adhesive effect of said adhesive being reduced in thearea in question prior to or during the detachment of the components.

The course of action that has been adopted up to now is that wafers areapplied to an elastic carrier film. Subsequently, these wafers areseparated into individual chips in a sawing process. This sawn wafer onthe carrier film defines together with a support frame the startingmaterial for the so-called die bonding processes. For detaching thechips from the carrier film, a needle, the so-called die ejector, isfirst moved, from the back, to a position below the chip to be detached;this die ejector detaches the chip from the carrier film from below. Thethus detached chip is picked up by a vacuum pipette and transferred toanother substrate, where the chip is then subjected to furtherprocesses. JP-A-2039452, for example, discloses a method wherein, inaddition to the above-mentioned features, the adhesive of the carriermaterial is weakened by the influence of a heat source, so as to improvechip detachment.

This method proved to be very useful in the past; a prerequisite forthis method is, however, that the chip is comparatively rigid incomparison with the carrier film, so that the ejector needle acting fromthe back will stretch the carrier film but nevertheless raise the chip.

It is the object of the present invention to provide a method with theaid of which also thinner chips can be singulated, i.e. also chips whoseown behaviour is similar to that of a film.

These are especially silicon chips having a thickness of less than 60 μmdown to a thickness of 10 μm.

For achieving this object, the method according to the present inventionis so conceived that the carrier is implemented as a rigid board,preferably a board of glass, glass ceramics or plastic material, theadhesive being deactivated in the respective area of the compositestructure prior to the detachment of the components, and the componentin question being picked up exclusively by means of the vacuum pipette.

This method is advantageous insofar as, just as in the case of thehitherto known methods, vacuum pipettes can still be used for thepurpose of detaching and insofar as it is additionally possible todetach also thin chips, which have a high ductility and whose behaviouris similar to that of a film, in an easy manner without using a dieejector. The carrier can comprise a rigid board, preferably a board ofglass, glass ceramics or plastic material. Especially in cases where theheat is supplied through the carrier, it will be advantageous when thethermal conductivity of the carrier is better in a direction transverseto the carrier plane than in the direction of the carrier plane.Materials, especially glass ceramics, having these properties are knownto a sufficient extent; they are used e.g. for ceramic hobs. It alsoproved to be advantageous when the adhesive is implemented as a film.This will guarantee a uniform thickness of the adhesive on the carrier.

The carrier comprises a rigid board, preferably a board of glass, glassceramics or plastic material. Especially in cases where the heat issupplied through the carrier, it will be advantageous when the thermalconductivity of the carrier is better in a direction transverse to thecarrier plane than in the direction of the carrier plane. Materials,especially glass ceramics, having these properties are known to asufficient extent; they are used e.g. for ceramic hobs. It also provedto be advantageous when the adhesive is implemented as a film. This willguarantee a uniform thickness of the adhesive on the carrier. In thisrespect, it will be particularly advantageous when the selectivelydeactivated adhesive is heat soluble. It will then be particularlysimple to deactivate the adhesive in a specific area of the compositestructure by a purposeful application of heat, so as to detach theindividual components subsequently. In the case of particularly thincomponents, the heat used for deactivating the adhesive can be appliedthrough the respective component.

Alternatively, the heat for deactivating the adhesive can also beapplied through the carrier. This possibility will be useful e.g. incases where the components are not extremely thin or in cases where theyare heat-sensitive. A simple possibility of applying the heat is the useof hot air. It will, however, also be advantageous to apply the heat byheat radiation, e.g. by infrared or laser irradiation.

The electronic components are preferably silicon chips having athickness of from 10 μm to 60 μm.

In the following, the method will be explained in detail makingreference to a drawing, in which:

FIG. 1 shows a top view of a sawn wafer on a carrier board,

FIG. 2 shows a sectional view through the carrier board of FIG. 1 alongline II-II, and

FIG. 3 shows an enlarged view of a detail of FIG. 2 with a schematicrepresentation of two heat sources and of a vacuum pipette.

FIG. 1 shows a glass board 1 used as a carrier board for an already sawnwafer 2 which comprises a plurality of chips 3 that have already beenseparated from one another. Said wafer and chips, respectively, have athickness of less than 60 μm and a behaviour similar to that of a film.

As can be seen even more clearly from FIG. 3, the wafer 2 is glued ontothe glass board 1 with the aid of an adhesive film 4. The adhesive film4 is made of a heat-soluble adhesive, i.e. an adhesive which loses orstrongly reduces its adhesive properties when heated.

In the following, the method according to the present invention will beexplained in detail making reference to the drawing.

The glass board 1 has first applied thereto an adhesive film 4. Thewafer 2 in its entirety is then glued onto this adhesive film 4.Alternatively, it is also possible to glue the adhesive film first ontothe wafer 2 which is then glued onto the glass board with the adhesivefilm 4.

Following this, the wafer 2 on the glass board 1 is separated into theindividual chips 3. This is done in the usual way by sawing.

For singulating the individual chips 3, i.e. for detaching them, theadhesive film 4 is heated in the area of the wafer 2 from which theindividual chip 3 is to be removed. In FIG. 3, two different methods areshown for this purpose. In the left half of FIG. 3, the lower surface ofthe glass board 1 is heated by means of a radiation source 5 below thechip 3 to be removed. In this area, the adhesive film 4 will dissolve sothat the chip can be picked up and removed with the aid of aconventional vacuum pipette 6.

In the right half of FIG. 3, an alternative is shown. The heat is hereapplied from above, in this case with the aid of a hot-air nozzle 7,which is positioned above chip 3 to be removed. The heat penetrates thechip 3 and dissolves the adhesive of the adhesive film 4 therebelow. Thehot-air nozzle 7 is then displaced to the side, thus making room for thevacuum pipette 6, which will then pick up the chip in the usual way.

The chips removed by means of the vacuum pipette 6 can be subjected tofurther processing in the usual way, e.g. glued onto some othersubstrate or subjected to further processing in a subsequent die-bondingprocess.

Alternatively to the above-described method, it is also possible to heata large-area region of the carrier so that the adhesive will bede-activated in the area of a plurality of chips simultaneously.

1. A method of singulating electronic components from a compositestructure, in particular chips from a wafer, wherein the compositestructure is first glued onto a carrier and the components are separatedfrom one another, whereupon the components are detached from the carrierindividually or in groups making use of a vacuum pipette, the adhesiveeffect of the adhesive being adapted to be reduced selectively, theadhesive effect of said adhesive being reduced in the area in questionprior to or during the detachment of the components, wherein the carrieris implemented as a rigid board, preferably a board of glass, glassceramics or plastic material, the adhesive being deactivated in therespective area of the composite structure prior to the detachment ofthe components, and the component in question being picked upexclusively by means of the vacuum pipette.
 2. A method according toclaim 1, wherein the adhesive is heat-soluble.
 3. A method according toclaim 1, wherein the heat used for deactivating the adhesive is appliedsuch that it passes through the component.
 4. A method according toclaim 1, wherein the heat used for deactivating the adhesive is appliedsuch that it passes through the carrier.
 5. A method according to claim1, wherein the heat is applied by means of hot air.
 6. A methodaccording to claim 1, wherein the heat is applied by heat radiation. 7.A method according to claim 1, wherein the thermal conductivity of thecarrier is better in a direction transverse to the carrier plane than inthe direction of the carrier plane.
 8. A method according to claim 1,wherein the electronic components are silicon chips having a thicknessof from 10 μm to 60 μm.
 9. A method of singulating electronic componentsfrom a composite structure, in particular chips from a wafer, whereinthe composite structure is first glued onto a carrier, preferably acarrier made of glass, glass ceramics or plastic material, by means of aheat-soluble adhesive, and the electronic components are then separatedfrom one another, whereupon the adhesive effect of the adhesive iseliminated by heat application, and the electronic components aresubsequently removed one by one from the carrier by using exclusively avacuum pipette, wherein prior to removing an electronic component fromthe composite structure by means of the vacuum pipette, the adhesiveeffect of the adhesive is eliminated exclusively in the respective areaof said electronic component.
 10. A method according to claim 9, whereinthe adhesive is deactivated in the respective area of the electroniccomponent.
 11. A method according to claim 9, wherein the behaviour ofthe electronic components is similar to that of a film.
 12. A methodaccording to claim 10, wherein the heat used for deactivating theadhesive is applied such that it passes through the electroniccomponent.
 13. A method according to claim 10, wherein the heat used fordeactivating the adhesive is applied such that it passes through thecarrier.
 14. A method according to claim 9, wherein the heat is appliedby means of hot air.
 15. A method according to claim 9, wherein the heatis applied by heat radiation.
 16. A method according to claim 9, whereinthe thermal conductivity of the carrier is better in a directiontransverse to the carrier plane than in the direction of the carrierplane.
 17. A method according to claim 9, wherein the electroniccomponents are silicon chips having a thickness of from 10 μm to 60 μm.18. A method according to claim 9, wherein no die ejector is used.